Power control apparatus for hybrid vehicle

ABSTRACT

A power control apparatus for a hybrid vehicle ( 1 ), the hybrid vehicle including an internal combustion engine ( 11 ), a front motor-generator ( 12 ), and a transmission ( 13 ) which are connected to front wheels (Wf), and a rear motor-generator ( 14 ) which is connected to rear wheels (Wr) via a rear differential gear box (DR). A calculated value, which is obtained by subtracting a front output power F_POWER and an accessory output power DV_POWER from a battery output power limit B_LimPow is set as an rear output power limit R_LimPow. The smaller of a rear drive command R_PowCmd (which is set depending on the running state of the vehicle) and a rear output power limit R_LimPow is set as a new rear drive command R_PowCmd. Accordingly, a demanded motor output power can be obtained without increasing the size of the main battery ( 15 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power control apparatus for afour-wheel drive hybrid vehicle having an internal combustion engine anda motor as power sources.

2. Description of the Related Art

Conventionally, a power control apparatus for a hybrid vehicle is knownin the art, which, for example, includes an internal combustion engineas a power source for driving front wheels, an AC generator that isdriven by the internal combustion engine, an electrical energy storagedevice for storing electrical energy generated by the AC generator, anda motor that drives rear wheels by being supplied with electrical energyfrom the electrical energy storage device, and in which the amount ofgeneration by the AC generator is controlled depending on the differencebetween the rotational speeds of the front wheels and the rear wheels(see, for example, Japanese Unexamined Patent Application, FirstPublication No. Hei 11-318001).

Moreover, conventionally, a hybrid vehicle is known in the art, which,for example, includes an internal combustion engine for driving eitherthe front wheels or the rear wheels, a generator that is driven by theinternal combustion engine, and a motor that drives the other of thefront and rear wheels by being supplied with electrical energy from thegenerator, and in which a target torque of the motor is determineddepending on the difference between the rotational speeds of the frontwheels and the rear wheels, or depending on a depression amount of theaccelerator pedal (see, for example, Japanese Unexamined PatentApplication, First Publication No. 2001-177909).

In the above-mentioned power control apparatus for a hybrid vehicle,because the motor for the rear wheels is driven by merely being suppliedwith electrical energy from the electrical energy storage device, thecapacity of the electrical energy storage device must be increased, orthe output voltage of the electrical energy storage device must be madehigher in order to increase the output power of the motor. In such acase, problems are encountered in that the electrical energy storagedevice becomes large, and high tension elements become large.

Moreover, in the above-mentioned hybrid vehicle, because the motor fordriving either the front wheels or the rear wheels is driven by merelybeing supplied with electrical energy from the generator, the outputpower of the motor is limited by the maximum electrical power of thegenerator; therefore, a desired output power may not be obtained.

SUMMARY OF THE INVENTION

The present invention was conceived in view of the above circumstances,and an object of the present invention is to provide a power controlapparatus for a hybrid vehicle, which includes an internal combustionengine for driving either the front wheels or the rear wheels, a motorthat drives the other of the front and rear wheels, and an electricalenergy storage device that receives energy from and sends energy to themotor, and which enables obtaining a desired output power of the motorwithout increasing the size of the electrical energy storage device.

In order to achieve the above object, the present invention provides apower control apparatus for a hybrid vehicle including: an internalcombustion engine for driving either the front wheels or the rearwheels; a first motor-generator which is connected to an output shaft ofthe internal combustion engine; a second motor-generator which isconnected to the other of the front and rear wheels; an electricalenergy storage device which receives energy from and sends energy to thefirst and second motor-generators; and a control unit which isoperatively connected to the internal combustion engine, the first andsecond motor-generator, and the electrical energy storage device, andwhich includes: an electrical discharge amount calculation section forcalculating the electrical power dischargeable from the electricalenergy storage device; an electrical power calculation section forcalculating the electrical power being generated by the firstmotor-generator or for calculating the electrical power being suppliedto the first motor-generator; an output power command calculationsection for calculating an output power command for a powering operationof the second motor-generator; and an output power limiting sectionwhich is adapted to calculate the sum of the electrical powerdischargeable from the electrical energy storage device and theelectrical power being generated by the first motor-generator or thedifference between the electrical power dischargeable from theelectrical energy storage device and the electrical power being suppliedto the first motor-generator, to compare magnitudes of the sum or thedifference and of the output power command for the secondmotor-generator, and to set the smaller of the sum or the difference andthe output power command for the second motor-generator as a new outputpower command for the second motor-generator.

According to the power control apparatus for a hybrid vehicle configuredas described above, the second motor-generator can be operated using theelectrical power being generated by the first motor-generator inaddition to the electrical power dischargeable from the electricalenergy storage device. As a result, the front wheels or the rear wheelscan be driven by the second motor-generator with an output power whichis greater than the electrical power dischargeable from the electricalenergy storage device by the electrical power being generated by thefirst motor-generator. In other words, the output power of the secondmotor-generator can be greater, without increasing the size of theelectrical energy storage device, than in the case in which the secondmotor-generator is operated merely using the electrical powerdischargeable from the electrical energy storage device or theelectrical power being generated by the first motor-generator.

Moreover, the electrical power which can be supplied from the electricalenergy storage device and the first motor-generator to the secondmotor-generator, i.e., the sum of the electrical power dischargeablefrom the electrical energy storage device and the electrical power beinggenerated by the first motor-generator or the difference between theelectrical power dischargeable from the electrical energy storage deviceand the electrical power being supplied to the first motor-generator, iscalculated, and when the sum or the difference is smaller than theoutput power command for the second motor-generator, the output powercommand for the second motor-generator is limited by the output powerlimiting section. As a result, the second motor-generator can beoperated in a powering manner while the electrical energy storage deviceand the first motor-generator are preferably operated in such a mannerthat, for example, the electrical energy storage device is preventedfrom being over-discharged, and the first motor-generator is preventedfrom receiving an excessive electrical generation command.

The power control apparatus for a hybrid vehicle may further include asecond electrical energy storage device which is different from theelectrical energy storage device, and which is operatively connected tothe control unit. The control unit may further include a secondelectrical discharge amount calculation section for calculating theelectrical power being discharged from the second electrical energystorage device, and the electrical discharge amount calculation sectionmay be adapted to set a calculated value, which is obtained bysubtracting the electrical power being discharged from the secondelectrical energy storage device from the electrical power dischargeablefrom the electrical energy storage device, as a new electrical powerdischargeable from the electrical energy storage device.

According to the power control apparatus for a hybrid vehicle configuredas described above, at least the electrical power being discharged fromthe second electrical energy storage device can be supplemented by theelectrical energy storage device, and at the same time, the output powerof the second motor-generator can be increased while the electricalenergy storage device and the first motor-generator are preferablyoperated.

The power control apparatus for a hybrid vehicle may further include asecond electrical energy storage device which is different from theelectrical energy storage device, and which is operatively connected tothe control unit. The control unit may further include a secondelectrical discharge amount calculation section for calculating theelectrical power being discharged from the second electrical energystorage device, and a generation command calculation section which isadapted to obtain a calculated value by subtracting the output powercommand for the second motor-generator and the electrical power beingdischarged from the second electrical energy storage device from theelectrical power dischargeable from the electrical energy storagedevice, and to set the absolute value of the calculated value as ageneration command for a generating operation of the firstmotor-generator when the calculated value is negative.

According to the power control apparatus for a hybrid vehicle configuredas described above, when the sum of the output power command for thesecond motor-generator and the electrical power being discharged fromthe second electrical energy storage device is greater than theelectrical power dischargeable from the electrical energy storagedevice, the electrical power being generated by the firstmotor-generator may be increased so that the output power of the secondmotor-generator and the electrical power being discharged from thesecond electrical energy storage device can be provided by theelectrical power dischargeable from the electrical energy storage deviceand the electrical power being generated by the first motor-generator.

The power control apparatus for a hybrid vehicle may further include adeterioration detecting device for determining whether the electricalenergy storage device has deteriorated, and the control unit may furtherinclude an output power command setting section for setting the outputpower command for the second motor-generator in such a manner that, whenthe electrical power calculation section is calculating the electricalpower being generated by the first motor-generator, and whendeterioration of the electrical energy storage device is detected by thedeterioration detecting device, the electrical power being generated bythe first motor-generator which is calculated by the electrical powercalculation section is set as the output power command for the secondmotor-generator.

According to the power control apparatus for a hybrid vehicle configuredas described above, when deterioration of the electrical energy storagedevice is detected, the output power command for the secondmotor-generator can be ensured by the electrical power being generatedby the first motor-generator.

The power control apparatus for a hybrid vehicle may further include asecond electrical energy storage device which is different from theelectrical energy storage device, and which is operatively connected tothe control unit. The control unit may further include a secondelectrical discharge amount calculation section for calculating theelectrical power being discharged from the second electrical energystorage device, and the output power command setting section may beadapted to set a calculated value, which is obtained by subtracting theelectrical power being discharged from the second electrical energystorage device from the electrical power being generated by the firstmotor-generator which is calculated by the electrical power calculationsection, as the output power command for the second motor-generator.

According to the power control apparatus for a hybrid vehicle configuredas described above, when deterioration of the electrical energy storagedevice is detected, the electrical power being discharged from thesecond electrical energy storage device in addition to the output powercommand for the second motor-generator can be ensured by the electricalpower being generated by the first motor-generator.

The present invention further provides a power control apparatus for ahybrid vehicle including: an internal combustion engine for drivingeither the front wheels or the rear wheels; a first motor-generatorwhich is connected to an output shaft of the internal combustion engine;a second motor-generator which is connected to the other of the frontand rear wheels; an electrical energy storage device which receivesenergy from and sends energy to the first and second motor-generators;and a control unit which is operatively connected to the internalcombustion engine, the first and second motor-generator, and theelectrical energy storage device, and which includes: an electricalcharge amount calculation section for calculating the electrical powerchargeable into the electrical energy storage device; an electricalpower calculation section for calculating the electrical power beinggenerated by the first motor-generator or for calculating the electricalpower being supplied to the first motor-generator; a regenerationcommand calculation section for calculating a regeneration command for aregenerating operation of the second motor-generator; and a regenerationlimiting section which is adapted to calculate the sum of the electricalpower chargeable into the electrical energy storage device and theelectrical power being supplied to the first motor-generator or thedifference between the electrical power chargeable into the electricalenergy storage device and the electrical power being generated by thefirst motor-generator, to compare magnitudes of the sum or thedifference and of the regeneration command for the secondmotor-generator, and to set the smaller of the sum or the difference andthe regeneration command for the second motor-generator as a newregeneration command for the second motor-generator.

According to the power control apparatus for a hybrid vehicle configuredas described above, the electrical energy storage device can be chargedusing the regenerated energy from the second motor-generator in additionto the electrical power being generated by the first motor-generator. Asa result, an amount of electrical energy, by which the electrical powerchargeable into the electrical energy exceeds the electrical power beinggenerated by the first motor-generator, can be provided by theregenerating operation of the second motor-generator. In other words,the regenerated energy from the second motor-generator can be greater,without increasing the size of the electrical energy storage device,than in the case in which the second motor-generator is operated in aregeneration manner merely depending on the electrical power chargeableinto the electrical energy storage device or depending on the electricalpower being supplied to the first motor-generator.

When the electrical power which can be supplied from the secondmotor-generator to the electrical energy storage device and the firstmotor-generator, i.e., the sum of the electrical power chargeable intothe electrical energy storage device and the electrical power beingsupplied to the first motor-generator or the difference between theelectrical power chargeable into the electrical energy storage deviceand the electrical power being generated by the first motor-generator issmaller than the regeneration command applied to the secondmotor-generator, the regeneration command for the second motor-generatoris limited by the regeneration limiting section. As a result, the secondmotor-generator can be operated in a regenerating manner while theelectrical energy storage device and the first motor-generator arepreferably operated in such a manner that, for example, the electricalenergy storage device is prevented from being over-charged, and thefirst motor-generator is prevented from being supplied with an excessiveelectrical power.

The power control apparatus for a hybrid vehicle may further include asecond electrical energy storage device which is different from theelectrical energy storage device, and which is operatively connected tothe control unit. The control unit may further include a secondelectrical discharge amount calculation section for calculating theelectrical power being discharged from the second electrical energystorage device, and the electrical charge amount calculation section maybe adapted to set a calculated value, which is obtained by adding theelectrical power being discharged from the second electrical energystorage device to the electrical power chargeable into the electricalenergy storage device, as a new electrical power dischargeable from theelectrical energy storage device.

According to the power control apparatus for a hybrid vehicle configuredas described above, the electrical power being discharged from thesecond electrical energy storage device can be provided by theregenerated energy from the second motor-generator; therefore, theregenerated energy from the second motor-generator can be increasedwhile the electrical energy storage device and the first motor-generatorare preferably operated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the general structure of a hybrid vehiclehaving a power control device for a hybrid vehicle according to anembodiment of the present invention.

FIG. 2 is a diagram showing the general structure of the power controldevice for a hybrid vehicle according to the above embodiment of thepresent invention.

FIG. 3 is a flowchart showing a control operation for calculating anoutput power limit that is applied to a powering operation of a rearmotor-generator.

FIG. 4 is a flowchart showing a control operation for calculating abattery output power limit.

FIG. 5 is a flowchart showing a control operation for limiting an outputpower command (i.e., a rear drive command R_PowCmd) that is applied tothe powering operation of the rear motor-generator.

FIG. 6 is a flowchart showing a control operation for calculating afront electrical generation limit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the power control device for a hybrid vehicle accordingto the present invention will be explained below with reference to theappended drawings. As shown in FIGS. 1 and 2, the power control device10 for a hybrid vehicle according to this embodiment is installed in afour-wheel drive hybrid vehicle 1 in which, for example, an internalcombustion engine (indicated by ENG in the drawings) 11, a frontmotor-generator (M/G1) 12, and a transmission (T/M) 13, which aredirectly connected to each other in series, are connected to frontwheels Wf via a front differential gear box DF, and a rearmotor-generator (M/G2) 14 is connected to rear wheels Wr via a reardifferential gear box DR. The power control device 10 includes a mainbattery (BATT) 15, a front power drive unit (PDU1) 16, a rear powerdrive unit (PDU2) 17, a DC-DC converter (DC-DC) 18, an auxiliary battery19, a battery ECU 21, a motor ECU 22, an engine and T/M ECU 23, and amanagement ECU 24.

In the hybrid vehicle 1, the driving powers of the internal combustionengine 11 and the front motor-generator 12 are transmitted to the frontwheels Wf via the transmission 13 such as an automatic transmission(A/T), a CVT, a manual transmission (M/T), or the like, and via thefront differential gear box DF which distributes the driving powerbetween the right and left front wheels Wf.

The driving power of the rear motor-generator 14 is transmitted to therear wheels Wr via the rear differential gear box DR which has a clutch(not shown), and which distributes the driving power between the rightand left rear wheels Wr.

When the clutch (not shown) provided in the rear differential gear boxDR is disengaged, the vehicle is placed in a front-wheel drive state inwhich solely the front wheels Wf are driven, and when the clutch isengaged, the vehicle is placed in a four-wheel drive state in which boththe front and rear wheels Wf and Wr are driven. In the four-wheel drivestate, distribution of the driving power between the right and left rearwheels Wr can be freely controlled.

Moreover, when power is transmitted in reverse from the front wheels Wfto the front motor-generator 12, and from the rear wheels Wr to the rearmotor-generator 14, such as when the hybrid vehicle 1 decelerates, themotor-generators 12 and 14 act as generators so as to generate so-calledregenerative braking force, whereby the kinetic energy of the vehicle isrecovered as electrical energy.

The powering operation and regenerating operation (generating operation)of the motor-generators 12 and 14 are controlled by the power driveunits 16 and 17 while receiving control commands from the motor ECU 22.

To the power drive units 16 and 17, each of which includes a PWMinverter that operates in a pulse width modulation mode, the highvoltage main battery 15, which receives energy from and sends energy tothe motor-generators 12 and 14, is connected. The main battery 15includes a plurality of modules which are connected to each other inseries, and each of which, as a unit, includes a plurality of cellswhich are connected to each other in series. Furthermore, the 12-voltauxiliary battery 19, which is provided for operating various electricalaccessories, is connected to the main battery 15 via the DC-DC converter18.

The DC-DC converter 18, which is controlled by the management ECU 24,steps down voltage between terminals of the main battery 15, or stepsdown voltage generated by the motor-generators 12 and 14 while beingcontrolled by the power drive units 16 and 17 in order to charge theauxiliary battery 19.

The power drive units 16 and 17, and the DC-DC converter 18 areconnected to the main battery 15 in parallel to each other.

The battery ECU 21 protects the main battery 15, calculates a state ofcharge SOC of the battery, and calculates the electrical powerdischargeable from the main battery 15 and the electrical power chargedinto the main battery 15. Moreover, the battery ECU 21 determineswhether or not the main battery 15 deteriorates depending on the stateof charge SOC, a measured voltage between the terminals of the mainbattery 15, the temperature of the main battery 15, past changes indischarged current and charged current, etc. To this end, the batteryECU 21 is provided with signals from a current sensor 25 for measuringcurrent flowing into and from the main battery 15, and signals from avoltage sensor (not shown) for measuring voltage between the terminalsof the main battery 15.

The motor ECU 22 controls the powering operation and regeneratingoperation of the motor-generators 12 and 14 in accordance with apowering torque command and a regenerating torque command which areinput from the management ECU 24.

The engine and T/M ECU 23 controls the operation of a fuel injectionvalve (not shown) for regulating an amount of fuel supply to theinternal combustion engine 11, the operation of a starter motor (notshown), ignition timing, and the gear change operation of thetransmission 13.

The management ECU 24 controls the operations of the battery ECU 21, ofthe motor ECU 22, of the engine and T/M ECU 23, and of the DC-DCconverter 18.

As will be explained later, the management ECU 24 calculates a rearoutput power limit R_LimPow, which is an output power limit applied tothe powering operation of the rear motor-generator 14, and sets anoutput power command (i.e., a rear drive command R_PowCmd) for thepowering operation of the rear motor-generator 14 based on, for example,a battery output power limit B_LimPow, which is the electrical powerdischargeable from the main battery 15, a front output power F_POWER,which is an output power from the front motor-generator 12, and anaccessory output power DV_POWER, and the management ECU 24.

To this end, the management ECU 24 is provided with signals from currentsensors 26 and 27 for respectively measuring current flowing into andfrom the power drive units 16 and 17.

The power control apparatus 10 according to the present embodiment isconfigured as explained above. Next, the operation of the power controlapparatus 10 will be explained.

The operation for calculating the output power limit applied to thepowering operation of the rear motor-generator 14 will be explainedbelow.

In step S01 shown in FIG. 3, criteria with regard to the state of chargeSOC, a measured voltage between the terminals of the main battery 15,the temperature of the main battery 15, and past changes in dischargedcurrent and charged current, which are used for determining whether themain battery 15 has deteriorated, are calculated.

In step S02, it is determined whether the main battery 15 hasdeteriorated based on the calculated criteria.

When the result of the determination is “YES”, the control operationproceeds to step S03, in which the battery output power limit B_LimPow,which is the electrical power dischargeable from the main battery 15, isset to be zero, and the operation proceeds to step S05, which will beexplained later.

In contrast, when the result of the determination is “NO”, the controloperation proceeds to step S04.

In step S04, the operation for calculating the battery output powerlimit is executed.

In step S05, PDU voltage V_FPDU, which is voltage between terminals ofthe main battery 15, is calculated based on, for example, signals fromvoltage sensor (not shown).

Next, in step S06, PDU current I_FPDU, which is input current suppliedto the front power drive unit 16, is calculated based on, for example,signals from the current sensor 26.

In step S07, a calculated value, which is obtained by multiplying thePDU voltage V_FPDU by the PDU current I_FPDU, i.e., the momentaryelectrical power being supplied to the front motor-generator 12, is setas the front output power F_POWER to be output by the frontmotor-generator 12.

Next, in step S08, battery current I_BATT, which is output currentoutput from the main battery 15, is calculated based on, for example,signals from the current sensor 25.

In step S09, PDU current I_RPDU, which is input current supplied to therear power drive unit 16, is calculated based on, for example, signalsfrom the current sensor 27.

In step S10, a calculated value, which is obtained by multiplying thePDU voltage V_FPDU by the PDU current I_RPDU, i.e., the momentaryelectrical power being supplied to the rear motor-generator 14, is setas the rear output power R_POWER to be output by the rearmotor-generator 14.

In step S11, a calculated value, which is obtained by multiplying thePDU voltage V_FPDU by the battery current I_BATT, i.e., the momentaryelectrical power being discharged from the main battery 15, is set as abattery output power B_POWER.

In step S12, a calculated value, which is obtained by subtracting thefront output power F_POWER from the battery output power B_POWER, i.e.,the momentary electrical power being discharged from the DC-DC converter18 is set as the accessory output power DV_POWER.

In step S13, a calculated value, which is obtained by subtracting thefront output power F_POWER and the accessory output power DV_POWER fromthe battery output power limit B_LimPow is set as the rear output powerlimit R_LimPow, which is an output power limit applied to the poweringoperation of the rear motor-generator 14, and the series of operationsis terminated.

The operation for calculating the battery output power limit in stepS04, which was mentioned above, will be explained below.

In step S21 shown in FIG. 4, an SOC output limit Plim_Soc is set byreferring to an SOC output limit (Plim_Soc) table, which defines outputlimit depending on the SOC of the main battery 15 (SOC output limitPlim_Soc).

In the SOC output limit (Plim_Soc) table, the SOC output limit Plim_Socis, for example, set so as to increase up to a predetermined upper limitin accordance with increase in the SOC of the battery.

Next, in step S22, a battery temperature output limit Plim_Tbat is setby referring to a battery temperature output limit (Plim_Tbat) table,which defines output limit depending on the temperature TBAT of thebattery (battery temperature output limit Plim_Tbat).

In the battery temperature output limit (Plim_Tbat) table, the batterytemperature output limit Plim_Tbat is, for example, set so as to be apredetermined upper limit when the temperature TBAT of the battery iswithin a predetermined range, so as to increase to the predeterminedupper limit in accordance with increase in the temperature TBAT of thebattery when the temperature TBAT of the battery is lower than thepredetermined range, and so as to decrease from the predetermined upperlimit in accordance with increase in the temperature TBAT of the batterywhen the temperature TBAT of the battery is higher than thepredetermined range.

Next, in step S23, a battery voltage output limit Plim_Vbat is set byreferring to a battery voltage output limit (Plim_Vbat) table, whichdefines output limit depending on the voltage VBAT between terminals ofthe main battery 15.

In the battery voltage output limit (Plim_Vbat) table, the batteryvoltage output limit Plim_Vbat is, for example, set so as to be apredetermined upper limit when the voltage VBAT of the battery is withina predetermined range, so as to increase to the predetermined upperlimit in accordance with increase in the voltage VBAT of the batterywhen the voltage VBAT of the battery is below the predetermined range,and so as to decrease from the predetermined upper limit in accordancewith increase in the voltage VBAT of the battery when the voltage VBATof the battery is above the predetermined range.

Next, in step S24, the SOC output limit Plim_Soc is set to the batteryoutput power limit B_LimPow which is the electrical power dischargeablefrom the main battery 15.

In step S25, it is determined whether the battery output power limitB_LimPow is greater than the battery temperature output limit Plim_Tbat.

When the result of the determination is “NO”, the operation proceeds tostep S27 which will be explained later.

In contrast, when the result of the determination is “YES”, theoperation proceeds to step S26.

In step S26, the battery temperature output limit Plim_Tbat is set tothe battery output power limit B_LimPow.

In step S27, it is determined whether the battery output power limitB_LimPow is greater than the battery voltage output limit Plim_Vbat.

When the result of the determination is “NO”, the series of operationsis terminated.

In contrast, when the result of the determination is “YES”, theoperation proceeds to step S28.

In step S28, the battery voltage output limit Plim_Vbat is set to thebattery output power limit B_LimPow, and the series of operations isterminated.

In other words, in the above-mentioned steps S21 to S28 in the operationfor calculating the battery output power limit, the least value amongthe SOC output, limit Plim_Soc, the battery temperature output limitPlim_Tbat, and the battery voltage output limit Plim_Vbat is set to thebattery output power limit B_LimPow.

Moreover, in steps S01 to S13, the output power limit applied to thepowering operation of the rear motor-generator 14 is set so as not toexceed an output power which is obtained by subtracting the front outputpower F_POWER from the battery output power limit B_LimPow, while on theother hand, at least the accessory output power DV_POWER is ensured bythe battery output power limit B_LimPow. As a result, the output powerof the rear motor-generator 14 can be sufficiently increased whilepreferably operating the main battery 15 and the front motor-generator14.

Next, the operation for limiting an output power command (i.e., a reardrive command R_PowCmd) that is applied to the powering operation of therear motor-generator 14 will be explained below.

In step S31 shown in FIG. 5, the rear drive command R_PowCmd, which isrequired for the powering operation of the rear motor-generator 14, iscalculated depending on, for example, the running state of the vehicle,etc.

Next, in step S32, the operation for calculating a front electricalgeneration limit, which will be explained later, is executed so that afront electrical generation limit F_LimGen, which is a limit ofelectrical power generated by the generating operation of the frontmotor-generator 12, is calculated.

Next, in step S33, when a calculated value, which is obtained bysubtracting the rear drive command R_PowCmd from the battery outputpower limit B_LimPow, is negative, the absolute value of the calculatedvalue is set as a front electrical generation command F_GenCmd which isrequired for the generating operation of the front motor-generator 12.In other words, when the battery output power limit B_LimPow is notsufficient for the rear drive command R_PowCmd and the accessory outputpower DV_POWER, the shortage of the power is supplemented by thegenerating operation of the front motor-generator 12.

In step S34, it is determined whether the front electrical generationlimit F_LimGen is greater than the front electrical generation commandF_GenCmd.

When the result of the determination is “YES”, the operation proceeds tostep S36 which will be explained later.

In contrast, when the result of the determination is “NO”, the operationproceeds to step S35.

In step S35, the front electrical generation limit F_LimGen is set tothe front electrical generation command F_GenCmd, and the operationproceeds to step S36.

In step S36, it is determined whether the rear drive command R_PowCmd isgreater than the rear output power limit R_LimPow.

When the result of the determination is “NO”, the series of operationsis terminated.

In contrast, when the result of the determination is “YES”, theoperation proceeds to step S37.

In step S37, the rear output power limit R_LimPow is set to the reardrive command R_PowCmd, and the series of operations is terminated.

Next, the operation for calculating a front electrical generation limitin step S32, which was mentioned above, will be explained below.

In step S41 in FIG. 6, an opening degree AP of the accelerator pedal,which relates to an amount of operation of the accelerator pedal by thedriver, is measured by, for example, an accelerator pedal opening degreesensor (not shown).

Next, in step S42, the vehicle speed Vcar is measured by, for example, avehicle speed sensor (not shown).

In step S43, a demanded driving power Fcmd_Req is set by referring to amap (a demanded driving power map) which defines the demanded drivingpower Fcmd_Req for the front wheels Wf depending on opening degree AP ofthe accelerator pedal and the vehicle speed Vcar.

Next, step S44, a gear ratio “Ratio” in the transmission is determined.

In step S45, a demanded engine power Pcmd_Req applied to the internalcombustion engine 11 is calculated based on the demanded driving powerFcmd_Req and the gear ratio “Ratio”.

Next, in step S46, an engine power limit LimEngPow is set by referringto an engine power limit (LimEngPow) table, which defines the enginepower limit of the internal combustion engine 11 depending on an enginerevolution rate NE of the internal combustion engine 11 (engine powerlimit LimEngPow) which is measured by a revolution rate sensor (notshown).

In the engine power limit (LimEngPow) table, the engine power limitLimEngPow is, for example, set so as to increase in accordance withincrease in the engine revolution rate NE of the internal combustionengine 11.

Next, in step S47, a calculated value, which is obtained by subtractingthe demanded engine power Pcmd_Req from the engine power limitLimEngPow, is set as the front electrical generation limit F_LimGen,which is a limit of electrical power generated by the generatingoperation of the front motor-generator 12, and the series of operationsis terminated.

In other words, in the above-mentioned steps S31 to S37, the smaller ofthe rear drive command R_PowCmd (which is set depending on the runningstate of the vehicle etc.) and the rear output power limit R_LimPow isset as a new rear drive command R_PowCmd.

According to the present embodiment of the power control device 10 for ahybrid vehicle, the output power of the rear motor-generator 14 can besufficiently increased without increasing the size of the main battery15 while preferably operating the main battery 15 and the frontmotor-generator 14, and while at the same time, the front output powerF_POWER and the accessory output power DV_POWER are ensured by thebattery output power limit B_LimPow.

In the above embodiment, the rear output power limit R_LimPow iscalculated based on the front output power F_POWER; however, the presentinvention is not limited to this, and, for example, the rear outputpower limit R_LimPow may be calculated based on an amount of generationin the front F_GEN, which is an amount of generation by the regenerativeoperation of the front motor-generator 12, and which is calculated basedon the output current from the front power drive unit 16.

In this case, in step S13 in the above embodiment, a calculated value,which is obtained by subtracting the accessory output power DV_POWERfrom a value obtained by adding the amount of generation in the frontF_GEN to the battery output power limit B_Lim_Pow, may be set as therear output power limit R_LimPow.

As a result, the output power of the rear motor-generator 14 can besufficiently increased without increasing the size of the main battery15 while preferably operating the main battery 15 and the frontmotor-generator 14 in contrast to the case in which the rearmotor-generator 14 is operated merely depending on the battery outputpower limit B_Lim_Pow, or merely depending on the amount of generationin the front F_GEN of the front motor-generator 12.

In addition to the above description about the operation for setting therear drive command R_PowCmd with regard to the above embodiment, theoperation for setting a regeneration command which is applied to therear motor-generator 14 will be explained below. In this case, insteadof the battery output power limit B_LimPow, a battery input power limitB_LimPin, which is the electrical power chargeable into the main battery15, may be calculated based on, for example, the SOC of the battery, thetemperature of the battery TBAT, and the voltage VBAT between terminalsof the main battery 15 (step T01). Moreover, instead of the front outputpower F_POWER in the above embodiment, for example, the amount ofgeneration in the front F_GEN, which is the amount of generation by theregenerative operation of the front motor-generator 12, may becalculated based on the output current from the front power drive unit16 (step T02).

A calculated value, which is obtained by adding the accessory outputpower DV_POWER to a value obtained by subtracting the amount ofgeneration in the front F_GEN from the battery input power limitB_LimPin, may be set as a regeneration limit which is applied to theregenerating operation of the rear motor-generator 14 (step T03), andthe smaller of a regeneration command applied to the regeneratingoperation of the rear motor-generator 14 (which is set depending on, forexample, the running state of the vehicle, etc. (step T04)) and theregeneration limit may be set as a regeneration limit applied to theregenerating operation of the rear motor-generator 14 (step T05).

When the generation command to be applied to the regenerating operationof the rear motor-generator 14 is set, and when the regeneration limitis set based on the front output power F_POWER instead of the amount ofgeneration in the front F_GEN, a calculated value, which is obtained byadding the accessory output power DV_POWER to a value obtained by addingthe front output power F_POWER to the battery input power limitB_LimPin, may be set as the regeneration limit which is applied to theregenerating operation of the rear motor-generator 14.

INDUSTRIAL APPLICABILITY

According to the power control apparatus for a hybrid vehicle of thepresent invention, the output power of the second motor-generator can begreater, without increasing the size of the electrical energy storagedevice, than in the case in which the second motor-generator is operatedmerely using the electrical power dischargeable from the electricalenergy storage device or the electrical power being generated by thefirst motor-generator.

Moreover, the second motor-generator can be operated in a poweringmanner while the electrical energy storage device and the firstmotor-generator are preferably operated in such a manner that, forexample, the electrical energy storage device is prevented from beingover-discharged, and the first motor-generator is prevented fromreceiving an excessive electrical generation command.

According to another power control apparatus for a hybrid vehicle of thepresent invention, at least the electrical power being discharged fromthe second electrical energy storage device can be supplemented by theelectrical energy storage device, and at the same time, the output powerof the second motor-generator can be increased while the electricalenergy storage device and the first motor-generator are preferablyoperated.

According to another power control apparatus for a hybrid vehicle of thepresent invention, the output power of the second motor-generator andthe electrical power being discharged from the second electrical energystorage device can be provided by the electrical power dischargeablefrom the electrical energy storage device and the electrical power beinggenerated by the first motor-generator.

According to another power control apparatus for a hybrid vehicle of thepresent invention, when deterioration of the electrical energy storagedevice is detected, the output power command for the secondmotor-generator can be ensured by the electrical power being generatedby the first motor-generator.

According to another power control apparatus for a hybrid vehicle of thepresent invention, when deterioration of the electrical energy storagedevice is detected, the electrical power being discharged from thesecond electrical energy storage device in addition to the output powercommand for the second motor-generator can be ensured by the electricalpower being generated by the first motor-generator.

According to another power control apparatus for a hybrid vehicle of thepresent invention, the regenerated energy from the secondmotor-generator can be greater, without increasing the size of theelectrical energy storage device, than in the case in which the secondmotor-generator is operated in a regeneration manner merely depending onthe electrical power chargeable into the electrical energy storagedevice or depending on the electrical power being supplied to the firstmotor-generator.

Moreover, the second motor-generator can be operated in a regeneratingmanner while the electrical energy storage device and the firstmotor-generator are preferably operated in such a manner that, forexample, the electrical energy storage device is prevented from beingover-charged, and the first motor-generator is prevented from beingsupplied with an excessive electrical power.

According to another power control apparatus for a hybrid vehicle of thepresent invention, the electrical power being discharged from the secondelectrical energy storage device can be provided by the regeneratedenergy from the second motor-generator; therefore, the regeneratedenergy from the second motor-generator can be increased while theelectrical energy storage device and the first motor-generator arepreferably operated.

1. A power control apparatus for a hybrid vehicle comprising: aninternal combustion engine for driving either the front wheels or therear wheels; a first motor-generator which is connected to an outputshaft of the internal combustion engine; a second motor-generator whichis connected to the other of the front and rear wheels; an electricalenergy storage device which receives energy from and sends energy to thefirst and second motor-generators; and a control unit which isoperatively connected to the internal combustion engine, the first andsecond motor-generator, and the electrical energy storage device, andwhich includes: an electrical discharge amount calculation section forcalculating the electrical power dischargeable from the electricalenergy storage device; an electrical power calculation section forcalculating the electrical power being generated by the firstmotor-generator or for calculating the electrical power being suppliedto the first motor-generator; an output power command calculationsection for calculating an output power command for a powering operationof the second motor-generator; and an output power limiting sectionwhich is adapted to calculate the sum of the electrical powerdischargeable from the electrical energy storage device and theelectrical power being generated by the first motor-generator or thedifference between the electrical power dischargeable from theelectrical energy storage device and the electrical power being suppliedto the first motor-generator, to compare magnitudes of the sum or thedifference and of the output power command for the secondmotor-generator, and to set the smaller of the sum or the difference andthe output power command for the second motor-generator as a new outputpower command for the second motor-generator.
 2. A power controlapparatus for a hybrid vehicle according to claim 1, further comprisinga second electrical energy storage device which is different from theelectrical energy storage device, and which is operatively connected tothe control unit, wherein the control unit further includes a secondelectrical discharge amount calculation section for calculating theelectrical power being discharged from the second electrical energystorage device, and wherein the electrical discharge amount calculationsection is adapted to set a calculated value, which is obtained bysubtracting the electrical power being discharged from the secondelectrical energy storage device from the electrical power dischargeablefrom the electrical energy storage device, as a new electrical powerdischargeable from the electrical energy storage device.
 3. A powercontrol apparatus for a hybrid vehicle according to claim 1, furthercomprising a second electrical energy storage device which is differentfrom the electrical energy storage device, and which is operativelyconnected to the control unit, wherein the control unit further includesa second electrical discharge amount calculation section for calculatingthe electrical power being discharged from the second electrical energystorage device, and a generation command calculation section which isadapted to obtain a calculated value by subtracting the output powercommand for the second motor-generator and the electrical power beingdischarged from the second electrical energy storage device from theelectrical power dischargeable from the electrical energy storagedevice, and to set the absolute value of the calculated value as ageneration command for a generating operation of the firstmotor-generator when the calculated value is negative.
 4. A powercontrol apparatus for a hybrid vehicle according to claim 1, furthercomprising a deterioration detecting device for determining whether theelectrical energy storage device has deteriorated, wherein the controlunit further includes an output power command setting section forsetting the output power command for the second motor-generator in sucha manner that, when the electrical power calculation section iscalculating the electrical power being generated by the firstmotor-generator, and when deterioration of the electrical energy storagedevice is detected by the deterioration detecting device, the electricalpower being generated by the first motor-generator which is calculatedby the electrical power calculation section is set as the output powercommand for the second motor-generator.
 5. A power control apparatus fora hybrid vehicle according to claim 4, further comprising a secondelectrical energy storage device which is different from the electricalenergy storage device, and which is operatively connected to the controlunit, wherein the control unit further includes a second electricaldischarge amount calculation section for calculating the electricalpower being discharged from the second electrical energy storage device,and wherein the output power command setting section is adapted to set acalculated value, which is obtained by subtracting the electrical powerbeing discharged from the second electrical energy storage device fromthe electrical power being generated by the first motor-generator whichis calculated by the electrical power calculation section, as the outputpower command for the second motor-generator.
 6. A power controlapparatus for a hybrid vehicle comprising: an internal combustion enginefor driving either the front wheels or the rear wheels; a firstmotor-generator which is connected to an output shaft of the internalcombustion engine; a second motor-generator which is connected to theother of the front and rear wheels; an electrical energy storage devicewhich receives energy from and sends energy to the first and secondmotor-generators; and a control unit which is operatively connected tothe internal combustion engine, the first and second motor-generator,and the electrical energy storage device, and which includes: anelectrical charge amount calculation section for calculating theelectrical power chargeable into the electrical energy storage device;an electrical power calculation section for calculating the electricalpower being generated by the first motor-generator or for calculatingthe electrical power being supplied to the first motor-generator; aregeneration command calculation section for calculating a regenerationcommand for a regenerating operation of the second motor-generator; anda regeneration limiting section which is adapted to calculate the sum ofthe electrical power chargeable into the electrical energy storagedevice and the electrical power being supplied to the firstmotor-generator or the difference between the electrical powerchargeable into the electrical energy storage device and the electricalpower being generated by the first motor-generator, to comparemagnitudes of the sum or the difference and of the regeneration commandfor the second motor-generator, and to set the smaller of the sum or thedifference and the regeneration command for the second motor-generatoras a new regeneration command for the second motor-generator.
 7. A powercontrol apparatus for a hybrid vehicle according to claim 6, furthercomprising a second electrical energy storage device which is differentfrom the electrical energy storage device, and which is operativelyconnected to the control unit, wherein the control unit further includesa second electrical discharge amount calculation section for calculatingthe electrical power being discharged from the second electrical energystorage device, and wherein the electrical charge amount calculationsection is adapted to set a calculated value, which is obtained byadding the electrical power being discharged from the second electricalenergy storage device to the electrical power chargeable into theelectrical energy storage device, as a new electrical powerdischargeable from the electrical energy storage device.